Unsteady Measurements of Periodic Effects in a Transonic Compressor With Casing Treatments

Flow structure in transonic blade tip region

Darmstadt transonic compressor

Axial slot geometry and instrumentation

Tip Injection geometry and instrumentation

Light sheet position in axial slots

Optical access to axial slots

Views through cavity window toward light sheet plane

Optical access to tip injection

Stereo PIV camera setup

WP contours at different operating points on design speedline

Local relative standard deviation of WP at NS operating points

Steady-state stereo PIV results for relative in plane mach number and radial mach number; interpolation in hidden areas; all CT–rotor and CT–IGV phases averaged for axial slot setup; comparison of detected shock position between PIV and WP measurements

Example of measured PIV data, derivation of vortex structure from radial velocity; operating point NSSC of smooth casing setup

Comparison of WP and PIV shock detection; variance of shock position depending on phase between rotor and CT increases toward lower mass flow

Time resolved injection process measured with phase locked PIV for axial slot configuration at NSAS operating point. The rotor is locked, CT travels upward; four time-steps from left to right; interpolation in hidden areas; all CT–IGV phases averaged.

Shock positions 17 revolutions before first stall cell for axial slots while closing throttle from NSAS to stall; variance of shock position increasing to ± 20% of blade spacing (t)

Shock positions 110 revolutions before first stall cell for axial slot configuration at design speedline; constantly closing throttle; unsteady WP measurements at 500 kHz sampling rate

Development of normalized recirculation velocity inside axial slots CT for different operating points on design speedline and before stall inception; measured via hot wire probe inside CT cavity